1. Field of the Invention
The present invention relates in general to a zoom lens optical system. More particularly, the present invention relates to a zoom lens optical system equipped with a light path changing prism for minimizing the size of a vertical type photographic device.
2. Description of the Related Art
Two types of moving image photographing devices are gunshot photographing devices and vertical photographing devices. Both devices are gaining popularity with customers. The gunshot type photographing devices are relatively larger in size than the vertical type photographing devices, but, it is easier for users to operate the gunshot type photographing devices. For instance, users can operate other functions of the devices while photographing. Typically, a user needs both hands to hold the device to photograph sharp and clear images. Alternatively, the vertical type photographing devices are convenient to carry and one hand is typically suitable to operate the device and photograph images at the same time. For convenience reasons, the vertical type photographing devices are more popular now.
Since the gunshot type photographing devices are more broadly used, commercialized photographing techniques are also more prevalent for the gunshot type photographing devices. This is also the reason that a vertical type photographing device shown in FIG. 1 uses a zoom lens optical system that is applicable to a gunshot type photographing device for photographing a subject.
Referring to FIG. 1, a conventional zoom lens optical system 100 includes a first lens group 110 for transferring an object to an image, a second lens group 120 for varying magnification, a third lens group 130 disposed at a distance from an iris diaphragm 100a to transfer the image of the object, and a fourth lens group 140 for focusing. Particularly, two dotted lines, a long dashed dotted line, and a long dashed double-dotted line represent light paths showing the image of the object.
However, the typical zoom lens optical system 100 is designed specifically for the gunshot type photographing device. Thus, there are limits to apply the zoom lens optical system 100 to the vertical type photographing device. That is, the zoom lens optical system 100 is so large that it is not suitably applied to the conventional vertical type photographing device because of its size. If the vertical type photographing device is increased in size, its attraction as a handy, convenient product is diminished. Thus, commercialization of the device is made more difficult. Meanwhile, the related art zoom lens optical system 100 includes four lens groups 110, 120, 130, and 140, so it cannot be applied to a CCD (Charge Coupled Device), which has a high number pixels, and does not deliver high-definition, high-resolution images.
Accordingly, there is a need for a zoom lens optical system capable of minimizing the size of a vertical type photographing device while delivering high-resolution images.